Nafion, the fluorinated membrane from DuPont has been intensively used for fuel cells as proton exchange membranes(PEMs). This polymer combines the mechanical strength and chemical/thermal stability with high proton conductivity and methanol permeability. In order to overcome methanol cross-over, the tortuous pathways can be introduced by dispersion of inorganic fillers. A Nafion membrane consists of an interconnecting network of nanoscopic aqueous domains surrounded by a fluorocarbon backbone. The size and extent of the aqueous domains or nanochannels control proton and methanol diffusion, and it is one of the factors controlling the maximum current densities generated by a cell. Understanding the effects of nanoclay addition on morphology of Nafion channels was the main aim of current study. In current research, organically modified montmorillonite(MMT) are introduced in Nafion, for reduction in methanol permeability. Nafion composite membranes were fabricated by ultra-sonic mixing and solution-casting method. Exfoliated structure of clay in polymeric matrix is approved by X-Ray Diffraction patterns. For membranes to be used in liquid DMFC, it is highly desirable to obtain the structural data of the electrolyte membranes at conditions close to that in practical fuel cells. Accordingly, we equilibrate the Nafion membranes with different MMT loading in methanol solution. The relationships between the Bragg spacing and the transport of methanol and protons in the nanocomposie membranes are discussed and the data are compared with those of Nafion117 as a commercial PEM. The proton conduction properties of the membranes have been investigated by impedance spectroscopy. The network cluster model is employed to retrieve the structural information from the scattering and proton conductivity data. While the nanocomposie membranes have narrower pathways for methanol/water permeation, the pure Nafion membranes have wider channels, resulting in higher methanol permeability.

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